Double wall connector segment for a gas turbine with cooling channels having concavities

A connector segment (22) for connecting a combustor liner (24) and a transition piece (20) in a gas turbine has a substantially cylindrical shape and is of double-walled construction including inner and outer walls (32, 34) and a plurality of cooling channels (36) extending axially along the segment, between the inner and outer walls (32,34). The cooling channels (36) are defined in part by radially inner and outer surfaces (40, 38), wherein at least one of the radially inner and outer surfaces (40,38) is formed with an array of concavities (42).